This invention relates to deflection and power supply circuits.
The horizontal oscillator of a television receiver provides switching signals to the trace switch of a horizontal deflection circuit for developing scanning current in a horizontal deflection winding. After the elapse of a start-up interval, rectified retrace pulses provide an energizing low B+ voltage to the oscillator. A start-up arrangement must therefore be provided to develop the low B+ voltage when the deflection circuit is inoperative.
A high B+ voltage of +120 volts DC, for example, may be provided by rectifying the secondary winding voltage of a power transformer. When operated at the horizontal deflection rate, the transformer may be of compact design. A power output switching stage provides the exciting voltage to the primary winding of the transformer. The horizontal oscillator provides horizontal rate drive signals which are transformer coupled to the switching elements of the power output stage.
The power supply voltage for the power output switching stage is obtained from rectified AC line mains voltage. The only portion of the described deflection and power supply circuit which is not conductively isolated from a mains supply terminal is the power output switching stage. By designing the power output switching stage to be self-oscillatory during the start-up interval, chassis mains isolation is retained while providing a start-up arrangement which is operative when the horizontal oscillator is not yet energized.